Genetic testing for Huntington’s disease
There are a few types of genetic tests that a person at risk for HD can take, including:
- a predictive test—which tests for the gene mutation in someone who isn't showing signs and symptoms
- a confirmatory test—which confirms an HD diagnosis in someone who is showing clinical symptoms
Your doctor will be able to recommend when to get a confirmatory test. However, the decision of whether or not to get a predictive test is a personal one and there is no “right” decision. Some people opt not to get tested because currently there is no disease-modifying treatment that stops or slows the progression of HD. Others decide to get tested so they can plan ahead before they develop symptoms. Each person must make the decision that is best for him or her. You may want to talk to your general physician, neurologist, or genetic counselor to discuss your options.
If you want to learn more about genetic testing so that you can make an informed decision, it may be a good idea to get it done at a place that is knowledgeable about HD. For example, some centers use the HDSA guidelines.
In addition to a genetic counselor, you may also want to talk with a social worker or psychologist to help process your thoughts about the test and results. If you get tested at a facility that uses the recommended HDSA guidelines, a mental health assessment is required before getting the genetic test.
With so many aspects of genetic testing to consider, it can be both overwhelming and confusing. However, there is a comprehensive checklist to help ensure that you are thinking about all of the pros and cons. This resource also includes topics like timing, impact, the testing process, and anonymous testing.
What do the genes mean?
Everyone has the huntingtin gene. HD is determined by the number of CAG repeats in the huntingtin gene. What really matters is how many CAG repeats someone has within that gene. A higher number of repeats can cause problems for you and your children, as shown in the table below. If you’re at risk for HD, speak to your neurologist if you are considering a genetic test.